The entire disclosure of Japanese Patent Application No. 2000-164107 filed on Jun. 1, 2000 including specification, claims, drawings and summary is incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates to a tunnel excavating machine for excavating and forming a tunnel in the ground and an excavation method therefor.
2. Description of the Related Art
Recently, upon excavating and forming a tunnel, reduction of construction period of the tunnel has been strongly demanded and high-speed construction thereof with a tunnel excavating machine has been an important theme.
For the reason, after the excavating machine main body such as a shield excavating machine is propelled by a stroke so as to excavate, the excavation is interrupted temporarily and then covering members are assembled. After this assembly, by applying propulsion reaction to the covering members again, the excavating machine is propelled. Instead of this type of the ordinary tunnel excavating machine, various types of tunnel excavating machines capable of allowing the covering members to be assembled under propulsion and excavation of the excavating machine main body have been developed.
For example, there is well known such a tunnel excavating machine, whose main body is divided into a front cylinder and a rear cylinder such that they are fit to each other retractably (telescopic) and while excavating by propelling the front cylinder with respect to the rear cylinder, segments are assembled in the rear cylinder at the same time.
Further, there is well known another tunnel excavating machine which is provided with a long (two strokes long) shield jack and assembly of the segments is started when excavation by a stroke is completed while excavation by a remaining stroke is carried out at the same time.
However, in the former tunnel excavating machine, in case where excavating a ground in which soil and water pressure apply, stopping of water at a retracting portion (fitting portion) of the front cylinder and the rear cylinder is indispensable so that a sealing mechanism is provided. However, because sand and soil enter into the retracting portion accompanied by that retracting motion, there is a problem that the sealing mechanism is damaged easily.
Further, in the latter tunnel excavating machine, because an erector for assembling the segments moves with the excavating machine main body, it moves relative to the existing segments. Therefore, there is another problem that positioning of the segment is very difficult.
The present invention has been achieved in views of the above described problems and an object of the invention is to provide a tunnel excavating machine of high-speed construction type and an excavation method which is capable of stopping water invasion completely and allows covering members to be assembled easily.
To achieve the above object, the present invention is directed to a tunnel excavating machine comprising: a cylindrical excavating machine main portion which is provided with a cutter head mounted rotatably at a front portion thereof and fit to an external periphery of a covering member through a sealing member; a cylindrical excavating machine auxiliary portion which is fit to the inside of the excavating machine main portion movably in the back and forth direction and provided with an erector for assembling the covering members; a plurality of main propulsion jacks disposed between the excavating machine main portion and the excavating machine auxiliary portion; and a plurality of auxiliary propulsion jacks mounted on the excavating machine auxiliary portion and capable of being retracted with respect to the covering member, wherein assembly of the covering members is enabled under propulsion and excavation with the excavating machine main portion.
Another feature of the present invention is that the plurality of the auxiliary propulsion jacks are connected to separate hydraulic pressure sources each having the same capacity through each of retractable selection valves.
Still another feature of the present invention is that the plurality of the auxiliary propulsion jacks are so controlled that at the time of extension motion, the plurality of the auxiliary propulsion jacks are controlled as a group, while at the time of retraction, each of the auxiliary propulsion jacks is controlled separately.
Further, the present invention provides a tunnel excavation method wherein, upon excavating and forming a tunnel with the aforementioned tunnel excavating machine, after executing a first step of, with a main propulsion jack extended from an initial position in which the main propulsion jack and an auxiliary propulsion jack are both retracted, propelling an excavating machine main portion, a second step of, with the auxiliary propulsion jack extended while retracting the main propulsion jack, propelling the excavating machine auxiliary portion, and a third step of, while propelling the excavating machine main portion with the main propulsion jack extended, retracting the auxiliary prolusion jack partially in succession so as to assemble covering members with an erector, the second step and the third step are repeated.